Potassium ion doped manganese oxide nanoscrolls enhanced the performance of aqueous zinc-ion batteries

Abstract

α-MnO₂ is a potential positive electrode material for aqueous zinc-ion batteries, but its electrochemical performance of zinc storage requires further improvement. In this paper, potassium ion-doped manganese dioxide nanoscrolls (KMnO₂) with oxygen vacancy were synthesized by a one-step hydrothermal method. It was observed that the electrochemical specific capacity was 250.9 mAh/g at a current density of 0.2 C, which was better than the existing commercial α-MnO₂. At a high current of 1 C, these batteries demonstrate improved cycle stability. Synchrotron radiation and other experiments as well as DFT theoretical calculations provided additional evidence that K doping was efficient in regulating the metal bond type and the mean charge regulation of covalent bonds with oxygen atoms in MnO₂. When MnO and MnK bonds are present, KMnO₂ showed outstanding adsorption of Zn²⁺ and further enhanced the Zn²⁺ embedding process. Simultaneously, oxygen defects caused by doping boosted the development of the nanoscroll structure, leading to an increase in active sites available for electrochemical reactions and subsequently enhancing the electrical conductivity of α-MnO₂. This study exhibits the potential of optimizing materials based on manganese with the introduction of a potassium doping strategy, resulting in improved performance for aquatic zinc-ion batteries, and presents novel perspectives for related research.